Childish Gambino, aka Donald Glover, made a surprise appearance at the iHeart Radio Music Festival to perform with Arianna Grande last night (Sept. 19) and took some time to speak with Billboard about the pair's collaboration and his new mixtape.

The rapper helped Grande out on her track "Break Your Heart Right Back" in front of a crowd in Las Vegas a day before his set at the festival. "The song was sent to us and we immediately were like, 'This is a hit,'" Gambino said. "She just sounds so good on it and it's a great song." The recording process sounds like it went just fine, too. "She came in when I was recording and was like, 'That's great. I love the tone of your voice,'" he added. "She knows her stuff about music and rap."

Gambino's next mixtape, STN MTN / KAUAI, is due out later this year via Gangsta Grillz, and the first single, "Sober," has people anxiously awaiting its arrival. "I feel like it's the first concept mixtape ever," he said about the effort. "It's a mixtape that goes into the EP but they're connected. It's the same character and the same story from Because the Internet and Camp. It's kind of like a nice in between for the next album."

In a recent interview with Hot 97, Gambino discussed his feelings about the state of rap. "I've talked about this before. Rap is done," he said. "Rap is done. I love hip-hop, I love rap, but the thing it was supposed to do it doesn't do anymore. It's not doing the social work it's supposed to do anymore."

Check out Billboard's interview with the rapper below.

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